Method of cutting tow

ABSTRACT

A cutting apparatus to cut a tow includes a tow support, first blade, and tow support deflector. The tow support supports the tow. The first blade cuts the tow. The tow support deflector is disposed in cooperative alignment with the first blade to exert a deflecting force upon the tow support. The deflecting force substantially prevents the first blade from striking the tow support.

FIELD OF THE INVENTION

The present invention generally relates to a cutting device. Moreparticularly, the present invention pertains to a blade arrangement fora tow cutting device and a system for use with the blade arrangement.

BACKGROUND OF THE INVENTION

Composite items are typically constructed from layers of material thatare laminated together. The categories of materials utilized tofabricate or ‘layup’ composite items includes, for example: fiber;fabric; tape; film; and foil. Within each of these categories, amultitude of diverse materials are utilized. For example, fibersutilized includes: glass; carbon; aramid; quartz; and the like. Whenthese fibers are arranged as woven sheets and unidirectional ribbons,they are referred to as fabric and tape, respectively.

Fiber placement is a process used to construct or fabricate compositeitems. These composite items include relatively simple planar sheets orpanels to relatively large complex structures. The composite items aregenerally built up from multiple layers or plies of composite materialsthat are pre-impregnated with uncured resin (“prepreg”). These plies areplaced on a form by a head that is positioned by a positioning devicesuch as a robotic arm or gantry.

Composite materials are typically supplied in rolls or spools in avariety of widths. Generally, more highly contoured composite items arefabricated from relatively narrower composite materials. Compositematerials having a width of about ⅛^(th) inch to about 1 inch aretypically referred to as “tow” and often, several strands of tow areplaced at once in order to lay down a wider strip or “course.” A head ona tow placement device arrays a group of prepreg tows into a continuousband and compacts them against the surface of the form or layup tool. Atthe end of each course, all of the tows are generally cut and thenrethreaded to start the next course. In addition, individual tows aresometimes cut during placement of a course to reduce the overall width,or shape, of the course. A disadvantage of conventional cutter modulesin tow placement devices is that the cutters often fail. Cutter failurestypically stop production until corrective measures are taken. Thesestoppages decrease laydown rates and increase product costs.

Another disadvantage of conventional cutter modules is that resin fromthe prepreg tows may foul the blades and other components of the cuttermodule. This fouling contributes to cutter failures and typicallyrequires cleaning procedures to be performed. These cleaning proceduresgenerally require the tow placement device to be shut down and mayrequire partial disassembly. Such procedures also decrease laydown ratesand increase product costs.

Accordingly, it is desirable to provide an apparatus and system capableof overcoming the disadvantages described herein at least to someextent.

SUMMARY OF THE INVENTION

The foregoing needs are met, to a great extent, by the presentinvention, wherein in one respect a device and system is provided thatin some embodiments improves the reliability of cutter modules in a towplacement device.

An embodiment of the present invention relates to a cutting apparatus tocut a tow. The cutting apparatus includes a tow support, first blade,and tow support deflector. The tow support supports the tow. The firstblade cuts the tow. The tow support deflector is disposed in cooperativealignment with the first blade to exert a deflecting force upon the towsupport. The deflecting force substantially prevents the first bladefrom striking the tow support.

Another embodiment of the present invention pertains to a tow placementsystem to fabricate a composite item with a tow. The system includes atow placement head, positioning device, and cutting apparatus. The towplacement head applies the tow to a tool. The positioning devicepositions the tow placement head. The cutting apparatus cuts the tow.The cutting apparatus includes a tow support, first blade, and towsupport deflector. The tow support supports the tow. The first bladecuts the tow. The tow support deflector is disposed in cooperativealignment with the first blade to exert a deflecting force upon the towsupport. The deflecting force substantially prevents the first bladefrom striking the tow support.

Yet another embodiment of the present invention relates to an apparatusto cut tow. The apparatus includes a means for supporting the tow, meansfor cutting the tow, and means for deflecting the supporting means tosubstantially prevent the cutting means from striking the supportingmeans.

Yet another embodiment of the present invention pertains to a method ofcutting a tow. In this method, the tow is supported on a support, thetow is cut with a blade, and the support is deflected to substantiallyprevent the blade from striking the support.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a laminating system according to anembodiment of the invention.

FIG. 2 is an exploded detailed view of the end effector suitable for usewith the laminating system of FIG. 1.

FIG. 3 is a detailed view of a cut/rethread module suitable for use withthe laminating system of FIG. 1.

FIG. 4A is a cross sectional view taken through line A-A of FIG. 3 of acutter configuration in a tow dispensing mode according to theembodiment of FIG. 1.

FIG. 4B is a cross sectional view taken through line A-A of FIG. 3 of acutter configuration in a tow cutting mode according to the embodimentof FIG. 1.

FIG. 4C is a cross sectional view taken through line A-A of FIG. 3 of acutter configuration in a tow rethreading mode according to theembodiment of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention will now be described with reference to the drawingfigures, in which like reference numerals refer to like partsthroughout. As shown in FIG. 1, a laminating system 10 suitable for usein an embodiment of the invention includes a tow placement head 12,positioning device 14, and form 16. The tow placement head 12 isconfigured to place a predetermined width of a tow 18 on the form 16.The tow 18 is typically stored on and dispensed from one or more spools20. A composite item 22 is fabricated by placing the tow 18 from thespools 20 onto the form 16 and then performing a curing procedure. Thecuring procedure is varied according the tow manufacturers'specifications. For example, curing bismaleimide (BMI) resins typicallyincludes subjecting a fabricated composite item to elevated heat andpressure.

The positioning device 14 includes any suitable device to position thetow placement head 12 or end effector relative to the form 16. Suitablepositioning devices include a robotic armature as illustrated in FIG. 1,gantry-type devices, and the like. In an embodiment of the invention,the positioning device 14 is a robotic armature or gantry-typepositioning device configured to control three to ten or more axes ofmovement. However, it is to be understood that the specific number ofaxes may depend upon the particular operating condition and thus, thenumber of axes controlled is not critical to the invention.

The form 16 includes any suitable form, tool, or mandrel for placing thetow 18 upon. The tow 18 is placed upon the form 16 in a plurality ofcourses 24 to generate a layer or ply 26. Generally, items such as thecomposite item 22 are fabricated from multiple plies 26. Typically, thesurface of the form 16, the courses 24 and/or plies 26 are referred toas a substrate 28 upon which subsequent courses of the tow 18 areplaced. As shown in FIG. 1, the form 16 is controlled to rotate about anaxis. When controlled to rotate thusly, the form 16 is typicallyreferred to as a mandrel. In other embodiments, the form 16 may bestationary or controlled to move in various axes. For example, the form16 may be secured to a sliding table or X-Y table. In this regard, theseand other embodiments in which the form 16 and/or the tow placement head12 are controlled to move, one relative to the other, are within thescope of the invention. Additionally, the movement of the form 16 andthe positioning device 14 both act to position the tow placement head 12relative to the form 16. Furthermore, the movement of the form 16 andthe positioning device 14 is generally coordinated to such a degree thatthe devices operate essentially as a single unit and thus, for thepurpose of this disclosure, modulation of the positioning device 14and/or the form 16 will be referred to with respect to the positioningdevice 14. Characteristics of the form 16, such as size, shape, contour,and the like, are based upon design parameters of the item 22.

FIG. 2 is an exploded detailed view of the tow placement head 12suitable for use with the laminating system 10 of FIG. 1. As shown inFIG. 2, the tow placement head 12 includes a main frame structure(“frame”) 30 and a plurality of components disposed along a tow path 32.The frame 30 is configured to provide support and connection points forthe plurality of components disposed along the tow path 32. The tow path32 basically includes a path from the spools 20, where the tow 18 isstored, to the form 16, where the tow 18 is placed. The plurality ofcomponents disposed along the tow path 32 include a pair of towalignment trays (“trays”) 40, a pair of index and key lock frames(“index frames”) 42, a pair of tow cutter/rethread modules 44, servodrive feed (“drive”) 46, and an application roller (“roller”) 48. It isto be noted that while an example is provided in which severalcomponents are present in pairs, in various other embodiments, some orall of the components are present as single, paired, or multiplecomponents and all such embodiments are within the scope of theinvention.

The trays 40 facilitate alignment of the tow 18. For example, each tray40 includes one or more channels 50 that guide the tow 18 to the roller48 via the drive 46 and the tow cutter/rethread modules 44. The channels50 include any suitable structure configured to retain the tow 18 inalignment. Suitable structures include, for example, channels, grooves,slots, combs, and the like. The channels 50 include a surface that iscompatible for use with the tow 18. For example, ultra high molecularweight plastic (“UHMW”) plastic is generally compatible with BMI andother resin systems. In some embodiments, all or most of the tray 40 isUHMW plastic. In other embodiments, the tray 40 includes a layer orcoating of UHMW plastic.

The trays 40 optionally include indexing points 54, drive windows 56 and58. If present, the indexing points 54 facilitate positioning the trays40 upon the frame 30. For example, as shown in FIG. 2, the indexingpoints 54 include notches configured to mate with respective tabs 60. Inanother example, the indexing points 54 include bores or pins configuredto mate with respective pins or bores. The drive windows 56 and 58 areoptionally included to provide an opening for the drive 46 to contactthe tow 18. In other instances in which, for example, the drive 46 isdisposed relatively above the channels 50, the drive window 58 may beomitted. Depending upon the configuration of the tow cutter/rethreadmodules 44, one or more cutter recesses are provided to facilitateproper operation of the tow cutter/rethread modules 44. That is, if someportion of the tow cutter/rethread modules 44 operate below the surfaceof the tray 40, the cutter recesses accommodate that the operation ofthe tow cutter/rethread modules 44. In other instances in which the towcutter/rethread modules 44 do not operate below the surface of the tray40, the cutter recesses may be omitted.

The index frames 42 facilitate securing respective ones of the trays 40to the frame 30. For example, the index frames 42 include one or morefasteners 62.

The tow cutter/rethread modules 44 are described in greater detailherein. In general, the tow cutter/rethread modules 44 cut, clamp,and/or rethread the tow 18. The tow cutter/rethread modules 44 includeone or more fasteners 70 to secure the tow cutter/rethread modules 44 tothe frame 30 and/or to secure the tow cutter/rethread modules 44 tointervening components.

The drive 46 is configured to engage the tow 18 and urge the tow 18along the tow path. In this regard, the drive 46 includes one or moreservo driven rollers 78. In addition, the drive 46 includes a fastener80 to secure the drive 46 to the frame 30.

The roller 48 provides a bearing surface to urge the tow 18 towards theform 16 and thereby apply the tow 18 upon the substrate 28.

In addition, the plurality of components disposed along the tow path 32are configured to function in a coordinated fashion to handle apredetermined width of the tow 18. According to design parameters of thecomposite item 22, this predetermined width includes ⅛^(th) inch, ¼inch, ½ inch, 1 inch, and the like. Similarly, components configured tohandle other width of the tow 18 are within the scope of variousembodiments of the invention.

FIG. 3 is a detailed view of a cut/rethread module 44 suitable for usewith the laminating system 10 of FIG. 1. As shown in FIG. 3 thecut/rethread module 44 includes a plurality of channels 92, rollers 94,cut/clamp frames 96, and blades 98. In operation, each of the pluralityof strips of the tow 18 is threaded along their respective channel 92,past the roller 94, and through the cut/clamp frame 96. The channel 92facilitates alignment of the tow 18. The roller 94, in variousembodiments is free rolling, rolls in one direction only, and/or iscontrolled to roll via a servo or other such actuator. Each of thecut/clamp frames 96 includes an actuator, as shown and described herein,to urge a respective blade 98 towards the tow cutter/rethread module 44and thereby cuts the respective tow 18 as the blade 98 passes throughthe tow 18. The blade 98 includes any suitably hard and wear-resistantmaterial. Suitable materials include metals such as carbide, steel andvarious alloys of steel, and non-metals such as ceramics and the like.

To rethread, the cut/clamp frame 96 is returned to the extended positionand roller 94 and/or the drive 46 is controlled to advance the tow 18.In this manner, some or all of the tows 18 are cut and rethread, in acontrolled fashion, according to design parameters of the composite item22.

It is to be noted that while FIG. 3 illustrates a cut/rethread module 44configured to operate with 6 or fewer strips of the tow 18, in variousembodiments, the cut/rethread module 44 is configured to operate withany suitable number of the tows 18. Suitable numbers of tow include 1,2, 3, 4, 6, 12, and the like.

FIGS. 4A-4C are cross sectional views taken through line A-A of FIG. 3of a cutter configuration in various modes according to the embodimentof FIG. 1. As shown in FIGS. 4A-4C, in addition to the blade 98, thecut/rethread module 44 optionally includes a blade 100 in co-operativealignment with the blade 98 and configured to assist or facilitate thecutting action of the blade 98. If present, the blade 100 includes asuitably hard and wear-resistant material. Suitable materials includemetals such as carbide, steel and various alloys of steel, andnon-metals such as ceramics and the like. The cut/rethread module 44further includes a tow support 102, tow support deflector 104, andactuator 106. The tow support 102 includes a sprung support surfaceconfigured to support the tow 18. The tow support 102 is configured todeflect in response to a force being exerted upon it. Suitable materialsfor the tow support 102 include spring steel, other resilient metals,plastics, and the like. Optionally, any surfaces of the tow support 102coming in contact with the tow 18 are configured to reduce buildup ofresin. For example, the tow support 102 is polished, chilled, and/orcoated with a substantially non-stick material. Suitable non-stickmaterials include UHMW plastic and the like. The actuator 106 isoperable to modulate the position of the cut/clamp frame 96 in responseto signals from a controller. In particular, the actuator 106 isoperable to draw the cut/clamp frame 96 relatively inwardly and returnthe cut/clamp frame 96 to an outward position.

As shown in FIG. 4A, the cut/rethread module 44 is in a tow dispensingmode. That is, the cut/clamp frame 96 is extended relatively outwardlyfrom the cut/rethread module 44. As such, the tow 18 is free to move ina direction 108.

FIG. 4B is a cross sectional view A-A of a cutter configuration in a towcutting mode according to the embodiment of FIG. 1. As shown in FIG. 4B,the tow support 102 includes a fastening arm 110 and a support arm 112that are joined at an intersection 114. In various embodiments, thesupport arm 112 is flexible or essentially ridged and the intersection114 is substantially ridged, flexible, or hinged. During the tow cuttingprocedure, the cut/clamp frame 96 is drawn in a direction 116 andrelatively towards the cut/rethread module 44 via the action of theactuator 106. Of note, the tow support deflector 104 is shown to exert adeflecting force upon the tow support 102 and causes the support arm 112to flex or otherwise move in a direction as the deflecting force istranslated through the tow 18. The tow support deflector 104 includes abearing surface disposed at or about at the level of the blade 98. Thatis, the tow support deflector 104 is disposed slightly above, at, orslightly below the blade 98. In a particular embodiment, when drawntowards the cut/rethread module 44, the tow support deflector 104contacts the tow 18 at or just prior to contact by the blade 98.Generally, the tow support deflector is configured to provide a force tourge the tow support arm 112 away from the blade 98. In this manner, thetow support deflector 104 substantially prevents the blade 98 fromcontacting the tow support arm 112. Optionally, the tow supportdeflector 104 operates in conjunction with the tow support arm 112 togenerate a clamping force upon the tow 18 as described herein.

As the blade 98 is drawn into the tow 18, any movement of the tow 18 inthe direction 108 urges the blade 98 in the direction 108. This urgingof the blade in the direction 108 generally acts to bring the blade 98towards the blade 100. It is an advantage of embodiments of theinvention that as the blade 98 passes by the blade 100, the closeproximity of the blade 98 to the blade 100 and the urging of the twoblades 98 and 100 together provides an efficient shearing action thatimproves cutting and/or reduces buildup of resin on the blades 98 and100. Upon completion of the cutting procedure, a portion of the tow 18that is downstream of the blade 98 is free to continue moving indirection 108 while a portion of the tow 18 that is upstream of the tow18 is essentially stopped until rethreading procedures are initiated.

The tow 18 is typically pulled or towed from the spool 20 and throughthe tow path 32 via the adhesion of the tow 18 to the substrate 28combined with the movement of the tow placement head 12 relative to theform 16. Therefore, when the downstream portion of the tow 18 is severedfrom the upstream portion of the tow 18, the upstream portion of the tow18 is controlled to stop via the action of a tow break and/or tends tostop of its own accord. In an embodiment, the tow support deflector 104is configured to directly urge the tow support 102. In this embodiment,essentially no clamping force is exerted upon the tow 18 via the actionof the tow support deflector 104 urging the tow support 102. Forexample, the tow support deflector 104 and the tow support 102 may bewider than the tow 18. In this example, the edges of the tow supportdeflector 104 and the tow support 102 may directly contact one another.More specifically, one or both of the tow support deflector 104 and thetow support 102 may include a protruding portion that facilitates directcontact between the tow support deflector 104 and the tow support 102without exerting a force upon the tow 18. In another embodiment, theforce exerted by the tow support deflector 104 further provides aclamping action upon the tow 18 disposed between the tow supportdeflector 104 and the tow support 102. That is, the tow supportdeflector 104 urges the tow 18 into the tow support 102 and therebydeflects the tow support 102. This clamping action facilitates retentionof the tow 18 within the respective channel 92 as shown in FIG. 3.

FIG. 4C is a cross sectional view A-A of a cutter configuration in a towrethreading mode according to the embodiment of FIG. 1. As shown in FIG.4C, the cut/clamp frame 96 has been returned to the tow dispensing modeposition as described in FIG. 4A. In response to an absence ofdeflective forces exerted by the tow support deflector 104, the supportarm 112 has returned to a tow dispensing position. That is, the supportarm 112 has returned to a level essentially in line with or veryslightly above the blade 100. As such, in response to being urgedforward by the drive 46, the cut end of the tow 18 is disposed toprogress over the blade 100 substantially without catching thereupon. Itis an advantage of various embodiments that the tow support deflector104, being level with or just below the level of the blade 98 inhibitscontact of the blade 98 by the tow 18 during rethreading and dispensingmodes. In addition, the tow deflector 104 further facilitatesrethreading by inhibiting an upward movement of the tow 18 that couldresult in a rethreading error.

Optionally, the cut/clamp frame 96 includes a lifting pin 120 thattraverses the cut/clamp frame 96 and provides a force to urge thesupport arm 112 into the tow rethreading and dispensing position.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention that fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

1. A method of cutting a tow comprising: passing the tow through a cut/clamp frame; drawing a first blade into the tow, the first blade including a free end having a different configuration than a free end of a tow support deflector located upstream of the first blade with respect to a movement direction of the tow; deflecting a tow support using the tow support deflector contacting a top surface of the tow without contacting the tow support prior to the first blade contacting the tow, the tow support deflector preventing the first blade from contacting the tow support; cutting the tow with a shearing action using the first blade moving relative to the second blade; rethreading the tow through the cut/clamp frame; and preventing upward movement of the tow using the tow support deflector when rethreading the tow through the cut/clamp frame, the tow support deflector and the first blade being separate components in contact with one another and being attached together and moving together.
 2. The method of claim 1 further comprising the steps of: supporting the tow on a tow support; and moving the tow along a direction of movement.
 3. The method of claim 1 wherein the step of deflecting the tow support further comprises: contacting a top surface of the tow without contacting the tow support prior to the first blade contacting the tow.
 4. A method of fabricating a composite item from tow using a tow placement head, the tow being stored on a spool, comprising the steps of: placing the tow on a form; moving the tow placement head relative to the form to pull the tow from the spool; supporting the tow on a support; moving the tow along a direction of movement; passing the tow through a cut/clamp frame; drawing a first blade into the tow, the first blade including a free end having a different configuration than a free end of a tow support deflector located upstream of the first blade with respect to a movement direction of the tow; deflecting the tow support using the tow support deflector contacting a top surface of the tow without contacting the tow support prior to the first blade contacting the tow, the tow support deflector preventing the first blade from contacting the tow support; cutting the tow with a shearing action using the first blade moving relative to a second blade; rethreading the tow through the cut/clamp frame; preventing upward movement of the tow using the tow support deflector when rethreading the tow through the cut/clamp frame, the tow support deflector and the first blade being separate components in contact with one another and being attached together and moving together; and performing a curing procedure to fabricate the composite item. 